1. Field of the Invention
The present invention relates to an ophthalmic photographing apparatus arranged to obtain a tomographic image or a front image of a given portion of an examinee's eye.
2. Description of Related Art
Conventionally, as an apparatus having a light scanning system and arranged to obtain a tomographic image or a front image of an examinee's eye, there is known an ophthalmic OCT (Optical Coherence Tomography) apparatus based on the principle of an optical coherence tomograph (see Japanese Patent Application Unexamined Publication No. 2008-29467) or a light scanning optometry apparatus based on the principle of a confocal optical system (an ophthalmic SLO (Scanning Laser Opthalmoscope). In this kind of apparatus, various noises could occur in the obtained image.
In general, if a noise occurs in an obtained image, a plurality of images obtained in one region are added, and pixel values are added and averaged. If a positional deviation occurs between the obtained images, the positional deviation between the obtained images is detected by comparing characteristic points of the obtained images and is corrected by moving on an image basis.
In the apparatus arranged to obtain the tomographic image or the front image of the eye by using the light scanning system as described above, fine movement of, the eye during scanning with measurement light due to involuntary eye movement or other reasons may generate a positional deviation in one obtained image. However, the above-described image addition method cannot deal with a local, fine positional deviation caused during the scanning with the measurement light. The addition without properly correcting the local positional deviation generally results in that a favorable image that is intended cannot be obtained.